A conventional vehicle intrusion monitoring system (for example, JP-A-11-328545) has a camera installed on the vehicle and the like to capture an image of an intruder when the vehicle is trespassed. A user of the system puts the system turned on to be in a watch state when the user leaves the vehicle. If any of the various types of onboard sensors detects an abnormality of the vehicle (opening of a door, break-in from a window etc.), the vehicle intrusion monitoring system captures an image by using a camera based on the assumption that the vehicle is trespassed. The captured image data is then transmitted to a base station.
Further, the other type of vehicle intrusion monitoring system (for example, JP-A-2002-157655) determines a trespassing based only on that a door lock is switched off for the first time, and a room lamp is turned on within three seconds of the switch-off of the door lock, while a watch state of the vehicle intrusion monitoring system is turned on.
However, intrusion detection in the conventional art is not necessarily satisfactory. That is, the camera of the vehicle intrusion monitoring system captures and transmits the captured image data even when an intruder is not in the vehicle, or when the intruder stops robbery on noticing the camera, or when a passer-by casually breaks a window without an intention of intrusion. In those cases, the captured and transmitted image does not provide a clue to the intruder.
As a consequence, the battery of the conventional system runs down by capturing and transmitting unnecessary image data, and incurs unnecessary expenditure on the user of the system when the transmission means uses a subscription service such as a telephone line. Moreover, the unnecessary captured image data is annoying for the user.
Further, the image area captured by the camera is not necessarily limited inside the vehicle, but also includes the outside of the vehicle through side windows, rear windows and the like. Thus, capturing an image of potential intruder around the vehicle by the camera upon detection of an abnormality of the vehicle can improve the usefulness of the vehicle intrusion monitoring system.